Apparatus for direct reduction of metal oxides



Feb. 14, 1967 c. A. TAYLOR 3,304,073

APPARATUS FOR DIRECT REDUCTION OF METAL OXIDES Original Filed Sept. 27. 1960 2 Sheets-Sheet 1 lim.

iNVENTOR. CHARLTON A. TAYLOR.

ATTORNEYS.

Feb. 14, 1967 c. A. TAYLOR 3,304,073

APPARATUS FOR DIRECT REDUCTION OF METAL OXIDES Original Filed Sept. 27. 1960 2 hetS$he 2 {I l n INVENTOR. CHARLTON A. TAYLOR.

ATTO R N EYS,

United States Patent 3,304,073 APPARATUS FOR DIRECT REDUCTION OF METAL OXIDES Charlton A. Taylor, P.O. Box 435, Garrettsville, Ohio 44231 Original application Sept. 27, 1960, Ser. No. 58,671, now Patent No. 3,157,488, dated Nov. 17, 1964. Divided and this application Sept. 19, 1962, Ser. No. 271,532 4 Claims. (Cl. 266-18) This application is a division of my copending application Serial No. 58,671, filed September 27, 1960, now Patent No. 3,157,488 granted November 17, 1964, as a continuation-in-part of my now abandoned application Serial No. 746,820, filed July 7, 1958.

The present invention is concerned with direct reduction of metallic oxides by reaction at suitable temperatures with hydrogen or other reducing gases to obtain substantially pure metal. The invention is further concerned with a batch process for such reduction, which rocess is low in cost, short in the length of time required for each batch and flexible as to quantities of oxides handled by a given size of apparatus used in practicing the process.

Various processes have been previously tried for direct reduction of metallic ores using a gas to convert the oxide of the metal to the metal itself. None, however, are commercially in use in the more industrially important countries because none have been found economically practical. This is chiefly caused by the fact that with such processes, the ores richest in the desired metallic oxides give the most efiicient rate of production, and such ores can be more economically reduced by other processes.

Reduction of such metallic ores by hydrogen has long been known to be potentially most desirable but also the most difficult process to use because of the heretofore unsolved problems of production in economical volumes, heating the ore to desired temperatures to obtain pure metal, obtaining complete deoxidization of the ore, the reversibility of the process in the presence of water vapor, and contamination by impurities found in the ore.

An object of the invention is to provide apparatus for practicing a batch type process for direct reduction of metal oxides with reducing gases producing substantially pure metal free from contamination by inpun'ties which are removed by volatilization during the reduction process.

Another object of the invention is to provide apparatus for practicing a batch type process for direct reduction of metal oxides utilizing low temperatures and prevention of those conditions creating a state of equilibrium.

Another object of the invention is to provide apparatus for practicing a bat-ch type process for direct reduction of metal oxides by reaction with suitable reaction gases wherein the metal oxide in finely divided form can be maintained in constant agitation within a confined area for obtaining the desired reaction and providing for control and removal of waste gaseous products of the reaction.

A further object of the invention is to provide apparatus which utilizes a substantially horizontal rotatably disposed reaction chamber adapted for handling varying amounts of powdered oxide with substantially uniform efiiciency in control of conditions relating to heating, exclusion of air, products of combustion and purity of the resulting metal.

A still further object of the invention is to provide apparatus of the type shown for economically and readily roasting or drying materials contained therein and removing vaporizable substances therein.

ice

These and other objects of the invention will be made apparent from the following description and the drawings forming a part thereof, wherein:

FIG. 1 shows a plan view of a modified form of apparatus for practicing the invention;

FIG. 2 shows a side elevation of the apparatus of FIG. 1;

FIG. 3 shows a side elevation partly in cross-section of only the furnace of FIG. 2;

FIG. 4 shows a cross-section on lines IV-IV of FIG.

FIG. 5 shows a fragmentary enlarged cross-section through the periphery of the furnace showing details of construction.

The apparatus of FIGS. 1 to 5 inclusive disclose a preferred form of furnace which may be used to directly reduce metal oxides by means of any suitable gaseous reductant to provide metal in finely divided form and free of substantially all contaminants which may be displaced by volatilization, including silica. This latter apparatus may also be used as an effective roasting or dehydration means independently of the direct reduction features.

Due to the rapidly approaching depletion of all known large deposits of lump magnetite ores, the steel industry is extensively engaged in searching for means whereby the remaining large quantities of high grade ore fines of both magnetite and hematite can be utilized in the production of iron for steel manufacture and to meet the increasing demands for high purity powdered iron. Likewise many low grade ore fines are available for these purposes, but must be beneficiated in some manner to be usable. Many new processes have been developed to both beneficiate the low grade ores by removal of much of the gangue and to convert the beneficiated fines into agglomerates by pelletizing and briquetting.

By use of the furnace of FIGS. 1 to 5 of the drawing these iron oxide fines, of varying iron content, can be readily and economically reduced to metal by a batch process, limited in volume only by the sizes of the furnace employed.

Due to the observed efficiency of the present type apparatus, larger particle sizes in the range from +10 to can be economically processed in the furnace of FIG. 3, although possibly of lesser purity and freedom from contaminants than in the case of smaller particle sizes of 100- to 500 mesh sizes. In these latter particle sizes much of the silica is of such small size as to pass off with the water vapor and substantially all of the sulphur and phosphorous is removed before reduction.

As shown in FIGS. 1 and 5, a cylindrical furnace 101 is suspended for rotation upon hollow stub axles 102 and 103 suitably journaled in bearings 104 mounted upon suitable bearing stands 105. Rotary motion is imparted to the furnace by any suitable means such as motor 106 and speed reducer 107. Suitable sprockets 108 on the speed reducer and 109 on the shaft 103 may be connected by a suitable drive chain 110.

Adjacent the furnace shaft 102 may be provided suitable storage of reducing gases and purging gases, for purposes of illustration, portable gas storage cylinders 111 of H 112 of N and 113 of A are shown. Both nitrogen and argon gases have been selected as inert gases for purging purposes, either may be used as desired. Suitable piping may be provided to discharge the stored gas from the cylinders into the furnace 101 through shaft 102. As shown, a pipe 114 extending transversely of cylinders 111, 112 and 113 has another pipe 115 connected thereto and branch pipes 116, 117 and 118 extending from 114 to connection with said cylinders. Each branch pipe has intermediate its ends a suitable flow meter 119 and a suitable valve 120 for registering flow of gas from its respective cylinder. Pipe 115 has a suitable check valve 121 intermediate its ends. The free end of pipe 115 is provided with a suitable elbow 122 and an extension therefrom into adjacent shaft 162. The extension of pipe 115 has a suitable swing joint connection 123 with the opening end of shaft 102 which serves to close the end of the shaft and permit relative rotary movement between the shaft 102 and pipe extension therein. At the opposite end of furnace 101, the shaft 163 has its outer end closed by a swivel joint member 124 having extending therethrough an exhaust pipe 125 having connected therewith an exhaust means (not shown). The exhaust pipe 125 has its inner end extending within the shaft 103 in communication with the interior of furnace 101. The outer end of the exhaust pipe 125 has a suitable flow meter 12d mounted therein for registering the volume of gas and vapors removed from the furnace by an exhaust means (not shown).

The details of construction of furnace 1111 are best shown in FIGS. 3, 4- and of the drawing. The inner peripheral shell 127 is perferably of suit-able material, such as a high nickel content steel, to stand temperatures up to 1200 to 1500 F. and is closed by suitable end walls 128 of similar metal. Preferably the joints between them are welded. Each end wall 128 is preferably reinforced by a suitable spider 129 through which end wall 128 extends the shafts 102 and 103. Enclosing the furnace inner shell is a similarly shaped jacket member 130 disposed in spaced relation to the inner shell providing a heating zone 131 therebetween. Mounted within the heating zone 131 and in spaced relation to both the jacket 13% and furnace inner shell 1.27 are electrical heating elements 132. These are preferably angularly spaced about the furnace inner shell so as to provide substantially uniform heating of the periphery of the furnace inner shell. One form of suitable heating elements is shown in FIGS. 4 and 5 wherein the element is of elongated U-sh'ape with the free ends 133 angularly offset and extending through the jacket. Suitable means such as 134 may be employed to secure the heating elements in fixed relation to the jacket 130. Enclosing the jacket 130 and in spaced relation thereto is a furnace outer shell 135 comprised of cylindrical side walls andcircular end walls. Between the jacket and outer shell is placed a suitable layer of insulation 136 so as to retain the heat from the heating elements within the heating zone 131. It will be noted that the ends 133 of the heating elements extend outwardly beyond the outer shell. Adjacent each outer shell end wall and surrounding the adjacent shafts 102 and 1113 may be suitable water cooling jackets 137. These jackets 137 retard transmission of heat through the shafts by conduction.

A suitable opening 138 is provided in the top wall of furnace 101 for admission of metal oxide to the furnace. A suitable circular collar 139 is mounted in opening 138 and provided with a central opening 140 which is closed by a movable closure member 141. A suitable stand 14-2 is mounted on collar 139 and is provided with a top wall 143. A suitable air cylinder 144 is mounted on top wall 143 and is provided with a depending piston 145 connected with closure member 141 for raising and lowering the latter. Above furnace 101 and adjacent the filling opening may be mounted any suitable form of ore storage bin 155 (FIG. 2), equipped with any well known form of vibrator, for feeding measured quantities of metal oxide into the furnace, after closure member 141 is raised for this purpose.

Within furnace 101 are mounted suitable baffle memeach having their opposite ends connected with the inner shell end walls 128 and their longitudinal lower edge connected to the periphery of the inner shell side walls 127 at opposite sides of the vertical center line of the furnace. The inner free ends of baffle portions 147 have connected thereto upwardly and inwardly triangular portions 148 which preferably connect with the furnace opening collar 139. These baffle portions 148 at opposite sides of the longitudinal center line of the furnace have their edge portions 149 and 15th connected by flat plate portions 151 and 152. In this manner the baffle 146 not only serves to turn and spread the oxide as the furnace rotates, but also provides a chute which discharges all the reduced oxide from the furnace through opening 141) after the furnace is stopped in an inverted position relative to that shown in FIG. 3 and the closure member 141 retracted from opening 140. At opposite sides of the longitudinal center line of furnace 101 and adjacent the bottom of the inner shell side wall 127 are triangularly shaped bafiies 153 and 154. These latter battles are suitably connected to the inner face of the side wall 127 and preferably extend continuously between the inner shell end walls 128.

The apparatus of FIGS. 1 to 5 is intended to be equipped with suitable forms of well known types of controls to provide complete automatic control of temperature within the heating zone between the furnace inner shell and the jacket and also within the inner shell of the furnace. After a charge of metal oxide within the furnace has been sufficiently dehydrated the subsequent sequence of steps of semi-reduction, removal of water vapor, completion of reduction and purging of the reduced metal and furnace interior as well 'as discharge of the furnace contents, may be automatically carried out.

By reason of the insulated heating zone 131 and uniform heating of the furnace inner shell, the metal oxide within the inner shell may be rapidly raised to temperatures up to about 1000 F. to drive off water from the oxide and remove same through exhaust pipe prior to beginning the reduction cycle. During such initial heating the sulphur and phosphorous within the oxide is volatilized and is removed with the water vapor before reduction begins, thereby preventing these contaminants from being re-absorbed by the newly reduced metal. Preferably, in addition to automatic controls, thermocouples placed in the heating zone and within the furnace may be used to actuate the controls to maintain a high temperature within the furnace during oxide dehydration and a reaction temperature of about750 F. before reduction is commenced. The baffles within the furnace, during reverse rotation thereof, spread and tumble the ore about for contact with the reducing gas. The baffles also serve to turn and spread the ore over and adjacent heated inner walls of the shell. The bafilcs themselves are also heated by conduction due to attachment to the inner shell walls.

I claim:

1. Apparatus for batch reduction of finely divided metal oxides to metal by means of a gaseous reductant, comprising a heating and reducing chamber having a hollow cylindrical metal inner shell and end closure walls, a similarly shaped jacket enclsing said inner shell and in spaced relation thereto providing a heating zone, a layer of insulating material overlying said jacket side and end walls, an outer shell enclosing said insulation, electrical resistance heating elements disposed within said space between said inner shell and jacket, said heating elements having portions extending outwardly through said jacket and outer shell for attachment of current supply lines, an opening in the top wall of said chamber, means for covering and uncovering said opening, a baffle member disposed within the upper portion of said inner shell and having converging portions embracing the top openside wall below said first-named baffie and at each side of the vertical center line of said inner shell, each said latter bafile being connected to said inner shell side wall, means forming an opening through each end wall of said chamberconcentric with the longitudinal center line of the chamber, a hollow stu'b shaft mounted in each said chamber end Wall opening and extending outwardly from its respective end wall, and bearing means supporting each said axle for selective rotation of said chamber there-on.

2. Apparatus as defined in claim 1, wherein each said baffies are connected to the inner shell in heat conductive engagement, and each baflie has inclined self-clearing side walls for discharge of material therefrom as the chamber rotates upon its supporting axles and bearings.

3. Apparatus as defined in claim 1, wherein one of said st-ub axles has means connected therewith for selective feeding of measured quantities of gas into the chamber and the other said stub axles has means connected therewith for selectively exhausting gas vapors from said chamber.

4 Apparatus for batch reduction of finely divided metal Oxides to metal by means of gaseous reductant, comprising (a) means, including a horizontally elongated enclosure rotatable about its longitudinal axis, for receiving and heated a measured body of finely divided metal oxides,

(b) means engageable with each end of said elongated enclosure for supporting same during rotation and for selectively admitting a gaseous reductant to and withdrawing the reaction gases from said enclosure,

(0) means disposed in spaced relation about the inner periphery of said enclosure for lifting, spreading and tumbling said oxides in the presence of said gaseous reductant during said rotation of said enclosure,

(d) means on the outer periphery of said enclosure for selectively admitting, retaining and discharging said metallic oxides :and resulting metal from said enclosure, and

(e) means associated with said elongated enclosure supporting means for selectively imparting reciprocal rotary motion to said enclosure and selectively stopping same with the said oxides admitting and discharging means in position to receive and discharge said oxides and/or metal.

References Cited by the Examiner UNITED STATES PATENTS 242,647 6/1881 Holmes et al. 26624 X 789,303 5/1905 Wagner 26618 829,575 8/1906 Dawson 26624 X 879,480 2/ 1908 Von Maltitz. 1,246,576 11/1917 Fiske 26618 2,393,467 1/1946 Hanak 26618 2,414,718 1/1947 Christensen 261111 2,648,535 8/ 1953 Ramsay et al. 26624 2,689,715 9/1954 Ericson 261111 2,964,309 12/1960 Rouaux 26624 CHARLIE T. MOON, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,304,073 February 14, 1967 Charlton A. Taylor in the above numbered pat- It is hereby certified that error appears ent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line 61, for "enclsing" read enclosing column 5, line 26, for "heated" read heating Signed and sealed this 17th day of Octoberl967 (SEAL) Attest: Edward M. Fletcher, Jr. EDWARD J. BRENNER Commissioner of Patents Attesting Officer 

4. APPARATUS FOR BATCH REDUCTION OF FINELY DIVIDED METAL OXIDES TO METAL BY MEANS OF GASEOUS REDUCTANT, COMPRISING (A) MEANS, INCLUDING A HORIZONTALLY ELONGATED ENCLOSURE ROTATABLE ABOUT ITS LONGITUDINAL AXIS, FOR RECEIVING AND HEATED A MEASURED BODY OF FINELY DIVIDED METAL OXIDES, (B) MEANS ENGAGEABLE WITH EACH END OF SAID ELONGATED ENCLOSURE FOR SUPPORTING SAME DURING ROTATION AND FOR SELECTIVELY ADMITTING A GASEOUS REDUCTANT TO AND WITHDRAWING THE REACTION GASES FROM SAID ENCLOSURE, (C) MEANS DISPOSED IN SPACED RELATION ABOUT THE INNER PERIPHERY OF SAID ENCLOSURE FOR LIFTING, SPREADING AND TUMBLING SAID OXIDES IN THE PRESENCE OF SAID GASEOUS REDUCTANT DURING SAID ROTATION OF SAID ENCLOSURE, (D) MEANS ON THE OUTER PERIPHERY OF SAID ENCLOSURE FOR SELECTIVELY ADMITTING, RETAINING AND DISCHARGING SAID METALLIC OXIDES AND RESULTING METAL FROM SAID ENCLOSURE, AND (E) MEANS ASSOCIATED WITH SAID ELONGATED ENCLOSURE SUPPORTING MEANS FOR SELECTIVELY IMPARTING RECIPROCAL ROTARY MOTION TO SAID ENCLOSURE AND SELECTIVELY STOPPING SAME WITH THE SAID OXIDES ADMITTING AND DISCHARGING MEANS IN POSITION TO RECEIVE AND DISCHARGE SAID OXIDES AND/OR METAL. 